Brightness calibrates particle size in single particle fluorescence imaging

Area of Science:

• Materials Science
• Nanotechnology
• Photophysics

Background:

• Semiconductor polymer dots (Pdots) are crucial for advanced imaging.
• Accurate particle size quantification is essential for reliable single-particle studies.
• Existing methods may lack precision for highly bright Pdots.

Purpose of the Study:

• To develop a novel method for quantifying the particle size of highly bright Pdots.
• To investigate the relationship between Pdot size, brightness, and photobleaching behavior.
• To establish guidelines for selecting optimal Pdots for single-particle imaging and tracking.

Main Methods:

• Single-particle fluorescence imaging to assess brightness.
• Intensity statistics to determine the quadratic dependence of brightness on particle size.
• Analysis of photobleaching trajectories and photon counts.
• Development of a calibration curve for particle diameter quantification.

Main Results:

• A quadratic relationship between single-particle brightness and Pdot size was established.
• Particle diameter can be accurately quantified by comparing fluorescence intensity to a calibration curve.
• Photobleaching rates showed minimal dependence on particle size, with exceptions for blinking and rapid decay.
• Overall photon counts increase with Pdot size up to 30 nm, after which the trend deviates.

Conclusions:

• The developed method enables precise size quantification of highly bright Pdots.
• Pdot size significantly influences overall photon emission.
• Optimal Pdots for single-particle imaging and tracking applications are those with diameters less than or equal to 30 nm.